[parted-devel] [PATCH 0/4] Add ability to set GPT PMBR boot flag

[Keshav P R]

On Sun, Jan 29, 2012 at 00:44, Phillip Susi <psusi at ubuntu.com> wrote:
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> On 01/28/2012 01:23 PM, Brian C. Lane wrote:
>> We can't know for certain that there are not BIOS's that check to make
>> sure it isn't set. Since that is how the spec was written it is possible
>> that such a BIOS exists.
>
> I'm pretty sure we can actually, since such a bios wouldn't be able to boot Windows, or at least some Linux distributions that go ahead and set the flag because some bioses won't boot without it.  If such a bios were released, not being able to boot the de facto standard PC OS certainly would result in it being fixed very quickly.
>

The issue here is the UEFI spec specifically mentions "boot/active
flag should not be set on the 0xEE entry in PMBR. Any firmware that
*strictly* complies with the spec will ignore the drive or show
errors.

>> It would be alot easier to just set it, but then what do we do if we
>> find out that there are others expect it to be clear?
>
> Theoretically, then you would need to add a flag to switch it off.
>
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